The Azido Group

The two NH2 stretching vibrations of aminopyrazoles follow the Bellamy-Williams relation [r-jlNH) = 345.5-0.876r <,s(NH)] (76AHC(Sl)l) establishing the amino tautomeric structure of (91). Azidopyrazoles also show the Vs and Vas bands of the azido group. The... 

Azidopyrazoles (455) exist as such even when the azido group is at the 3-position where an azido-tetrazole equilibrium is possible (469) (470) (77AHC(2l)72, 78AHC(22)184). 

Relatively little work has been done on displacement of the azido group on benzenes ° (by hydroxide, ammonia, amines, or hydrazine) or on heterocycles. The latter involve reaction of... 

Among other bicyclic amidine catalysts, 3,4,6,7,8,9-hexahydro-2//-pyrido[l,2-n]pyrimidine was also applied in the preparation of /3-alkoxy nitriles from Q ,/3-unsaturated nitriles and alcohols (99GEP 19803515). The azido group could be smoothly converted into a trifluoroacetylamido group by treatment with (Cp3CO)2 in the presence of Ph3P and 2,3-dihydro-2//-pyrido[l,2-n]pyrimidin-2-one under Ar in THE (99HCA2380). 

Molar Refraction. The molar refraction of the azido group in alkyl azides was estd to be ca 9,4 (Ref 14). For a discussion of molar refraction see Ref 9, p 528... 

The chemistry of the azido group The chemistry of the acyl halides The chemistry of the carbon-halogen bond (2 parts)... 

The Chemistry of the Azido Group The Chemistry of Acyl Halides... 

Ketenes also add to imines in 2 + 2 cycloadditions giving the important g-lactams (20). The reglochemistry is predictable as the nitrogen is the nucleophilic atom in the imine. This is true even in conjugated imine (21) which gives (22) with azidoketene. The azido group can... 

Paulsen and his coworkers first synthesized (-f-)-203 from L-quebrachitol (286) by a 21-step reaction as follows. The di-O-isopropylidene derivative was oxidized to the ketone (287), and then epoxidized with dimethyl sulfox-onium-methylide to give 288, which was subjected to benzoylation, mesyla-tion, and demethylation, followed by benzylation, to afford 289. Introduction of unsaturation was accomplished by epoxidation of 289 with sodium methoxide to 290 and 291, and deoxygenation to 292. The azido group was introduced with azobis(dicarboxylate) to give 293, which was hydrogeno-lyzed, followed by deprotection to afford 203. 

Kuzuhara and his coworkers synthesized (+)-205 by hydroxylation of the alkene 304, which was prepared from the chiral azidocyclohexene derivative (303) derived from D-glucose, in which a novel rearrangement of the C - C double bond accompanying reduction of the azido group with lithium aluminum hydride was observed. 

The oxygen—carbon bond was also hydrogenolyzed during the reduction of the azido group (Scheme 4.152).591... 

Nitration of the diazido dinitro derivative 81 proceeds easily to give the 4,8-diazido-2,3,9,10-tetranitro derivative 82 in 76% yield (Equation 3). The ease of the nitration of 81 stems from activation of the C-3 and C-9 positions toward electrophilic attack by the ortho-directing effect of the azido groups <1996JOC5801>. 

A way to introduce the primary amino group directly onto the selenophene ring is via the azido compound, obtained by nucleophilic substitution of the bromo derivative with sodium azide. Useful transformations of the azido group are shown in Scheme 12.117 The amino aldehyde (109) is a suitable starting material for the preparation of selenolo[3,2-b]pyridine (110) by the Friedlander reaction.138 Not only can the azido be reduced to an amino... 

The synthesis of the D-gulonolactam 36 was based on an intramolecular cyclisation /ring enlargement strategy involving reduction of the azido group in 35 followed by intramolecular nucleophilic attack on the lactone moiety to afford 36 in excellent yield <06T7455>. 

Hong et al. (2004) also found that modification of PAMAM dendrimers with a short PEG linker arm could act to reduce nonspecificity caused by the amines on the dendrimer-modified surface. An azido-PEGj-aininc spacer was activated with nitrophenyl carbamate to yield an activated intermediate that could be used to modify the amines on the dendrimer (Figure 7.24). Reaction at high molar ratio resulted in about 61 PEG-azido spacers on the dendrimer. Reduction of the azido group to an amine using triphenylphosphine in THF provided the dendrimer-PEG-amine derivative for surface modification. The added presence of the PEG spacer arm reduced... 

As can be seen in Scheme 3.249, a-azido oximes (465) can be involved with advantage in the selective reduction of the azido group in the presence of the oximino fragment and also in the selective or nonselective reduction of the oximino fragment (525). 

PataiS (ed) (1972) Chemistry of the azido group. The chemistry of the functional groups. Interscience, New York... 

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